Optimization of Reactive Muffler Through Pressure Acoustic Analysis and Taguchi Approach

In the past few decades, automotive vehicles have increased drastically and due to this noise pollution has increased substantially and becoming hazardous for humans. This has put government to implement strict regulation on automotive manufacturers for keeping the noise levels within the specified limits. In context to that manufacturers are working hard in redesigning various components of automotive which are contributing in the overall sound of the vehicle, for instance engine components, transmission system, intake and exhaust system, cooling system and tires. In this study, attempt has been made to reduce the exhaust gases noise through muffler redesigning as exhaust sound contributing maximum to the overall sound level of automotive. Taguchi-based design of experiment methodology has been used to optimize the design and to improve the muffler capability. Initially two baffles were finalized instead of three baffles on the basis of formation of domes within certain frequency band obtained from pilot experiments carried out through pressure acoustic frequency domain analysis. Utilizing the two baffles, position of these baffles from inlet and outlet tube and position of hole were selected as the control parameters. Signal-to-noise ratio analysis for these trail experiments through Minitab gave us the optimized value of dimensions for achieving the maximum transmission loss. Analysis of variance (ANOVA) was then performed for predicting the significance and percentage contribution of the control parameters toward the performance of the muffler. The transmission loss test in impedance tube set up validates the transmission loss (TL) value for the optimized reactive muffler and both results showed good agreement between them with small variation in TL value. Finally, the obtained results for the optimized muffler were compared for the TL value of existing muffler obtained through simulation and experimentation. The optimized mufflers showed significant improvement in terms of maximum TL and better performance as a whole with widening of frequency band for the third dome. The study also proposed the pressure acoustic frequency domain analysis as an efficient methodology for determining the performance of muffler.